1. Field of the Invention
The invention relates to optical fiber sensors generally, and more specifically to Fabry-Perot optical fiber sensors, methods for making such sensors, and methods for multiplexing Fabry-Perot and other types of optical fiber sensors.
2. Discussion of the Background
Optical fiber sensors are becoming more popular for a wide variety of applications. Optical fiber sensors offer several advantages over other types of sensors such as electronic and mechanical sensors. Optical fiber sensors are generally more rugged and have longer lifetimes than these other types of sensors, are immune from electromagnetic interference, can often be made much smaller than these other types of sensors, and offer multiplexing capabilities.
One type of optical fiber sensor known in the art is the interferometric optical fiber sensor. An external Fizeau fiber optic sensor is described in U.S. Pat. No. 5,301,001 to Murphy et al. The sensor described in that patent is formed by placing two optical fibers in a silica tube separated by an air gap. When light is launched into one of the fibers, interfering Fresnel reflections caused by the air/fiber interfaces at the ends of the fibers are formed. Changes in the length of the cavity resulting from changes in temperature, pressure or mechanical strain on the optical fiber produce changes in phase between the reflections. This results in measurable changes in the amplitude of the reflected light. By measuring the changes in amplitude, the corresponding temperature/pressure/mechanical strain can be determined.